1. Field of the Invention
The present invention relates to a bandwidth control apparatus, a bandwidth control method, a bandwidth control system, and a bandwidth allocating apparatus for data transfer in a subscriber data transmission system, and, more particularly to a bandwidth control apparatus, a bandwidth control method, a bandwidth control system, and a bandwidth allocating apparatus applied to an x Digital Subscriber Line (x DSL: ‘x’ is a generic term representing ‘Asymmetric’, ‘Symmetric’, and ‘Very high-bit-rate’) and Fiber To The x (FTTX: ‘x’ is agenericterm representing ‘Building’, ‘Curb’, ‘Cabinet’, and ‘Home’).
2. Description of the Related Art
The x DSL uses a metallic cable such as a telephone line for a transmission medium serving as an access line to make it possible to perform high-bit-rate data transmission at several Megabits/second, and the FTTx uses an optical fiber cable for a transmission medium to make it possible to perform high-bit-rate data transmission at several tens Megabits/second to hundred Megabits/second.
In recent years, in the subscriber data transmission system using a metallic cable such as a telephone line for a transmission medium serving as an access line, the xDSL technique that makes it possible to perform high-bit-rate data transmission at several Megabits/second attracts attention. In particular, the Asymmetric Digital Subscriber Line (ADSL) attracts much attention. In the ADSL, data transfer bit rates are different in an upstream direction in which a data stream flows from a user terminal to a network and a downstream direction opposite to the upstream direction. This asymmetry is suitable for an access pattern of the Internet. According to the spreads of the ADSL, access lines are rapidly developed into broad bands.
A system constitution of a general data transmission network will be explained with reference to FIG. 1.
FIG. 1 is a diagram showing an example of a network constitution of an Internet connection service to which an Access Multiplexer (AM) is applied. In user premises, Personal Computers (PCs) 111 are connected to subscriber lines 109 serving as access lines via Customer Premises Equipment (CPE) 110. On a switching system side, an Access Multiplexer (AM) 106 that terminates the subscriber lines 109 from the respective user premises and concentrates signals on one high-bit-rate transmission signal 105 is provided.
A Line Termination Unit (LTU) 108 and an Integrated Gateway Unit (IGU) 107 are equipped in the access multiplexer 106. The integrated gateway unit 107 is an apparatus that multiplexes a signal and performs protocol conversion for the signal as required.
The high-bit-rate transmission signal 105 concentrated in the access multiplexer 106 is output to the Internet 103 through a switch or a router 104. The high-bit-rate transmission signal 105 output to the Internet 103 is further transferred to an Internet Service Provider (ISP) server 101 or the like through a switch or a router 102.
An Internet access pattern of a client/server type illustrated in FIG. 1 has a characteristic that upstream traffics are extremely small compared with downstream traffics. Therefore, conventionally, bandwidth control for the upstream traffic in the access multiplexer 106 has not been regarded as so important.
However, in recent years, a communication pattern by Peer to Peer (P2P) communication that connects between the personal computers is increasing. Thus, bandwidth assurance for the upstream traffics and fairness of traffic allocation among users are important.
As represented by the xDSL, a best effort service is often applied to access lines. Therefore, depending on a difference of conditions such as a state of the subscriber lines 109 serving as access lines to be transmission paths and performance of the personal computers 111 that are user terminals, effective rates usable in the respective personal computers 111 fluctuate. In other words, in the respective personal computers 111, an optimum effective rate corresponding to a line state at a certain point is applied. The personal computers 111 perform data communication using an effective rate usable at that point.
In general, in the downstream traffics, the high-bit-rate transmission signal 105 transmitted from the network 103 is often supplied to the respective subscriber lines 109 by a broadcast type transmission for transmitting signals to unspecified number of destinations. The broadcast type transmission uses bandwidth resources of the downstream traffics at the time of transmission collectively for all the access lines rather than separately for the individual access lines. Therefore, in the access multiplexer 106, it is unnecessary to perform bandwidth control of traffics for the respective subscriber lines 109. However, in the upstream traffics, signals transmitted from the subscriber lines 109 are transmitted separately and concentrated in the access multiplexer 106. When bandwidths of the high-bit-rate transmission signal 105 after concentration is limited by an upper limit value of a bit rate defined by interface with the network, it is necessary to perform the bandwidth control for traffics for each of the subscriber lines 109 in the access multiplexer 106 in order to control upstream signals flowing in from the subscriber lines 109.
Usually, the access multiplexer 106 allocates equal bandwidths to the respective subscriber lines 109. However, even if effective rates allocated for some subscriber lines 109 are not fully used and, as a result, there is still a room available for use in bandwidths of the high-bit-rate transmission signal 105 after concentration in the access multiplexer 106, this is not reflected on the allocation of bandwidths to the other subscriber lines 109.
Setting of bandwidths in the access multiplexer 106 is statically performed. Therefore, even if arbitrary users end communication and the subscriber lines 109 of the users have become idle, it is impossible to divert bandwidths allocated to the idle subscriber lines 109 to the subscriber lines 109 used by the other users. The reason why bandwidths are statically set and the users are treated fairly in this way is to simplify a constitution of the access multiplexer 106 and also to be based on an idea that the same level of services should be fairly provided to each user.
On the other hand, there is also an idea that it is preferable to faithfully reflect the conditions such as a state of the subscriber lines 109 and performance of the personal computers 111 on allocation of bandwidths for each subscriber line 109 and effectively use bandwidths of the high-bit-rate transmission signal 105 after concentration. However, in order to realize this idea, a constitution of the access multiplexer 106 is inevitably complicated.
As a related technical document, a technique concerning the xDSL entitled “Data Transmission Network” is disclosed in Japanese Patent Application Laid-Open No. 2004-519974, which is corresponding to the International Publication No. WO 02/089459 A1 of the PCT. This technology relates to a data transmission network for data transmission which allows xDSL data transmission and voice data transmission between a backbone network and a network termination device on any data transmission medium such as a copper telephone line. However, the document does not disclose a technique related to bandwidth control.